Chapter 10

Consider the reaction, \(2 \mathrm{~A}+\mathrm{B} \longrightarrow\) Products When concentration of alone was doubled, the half life did not change. When the concentration of \(A\) alone was doubled, the rate increased by two times. The unit of rate constant for this reaction is (a) no unit (b) \(\mathrm{mol} \mathrm{L}^{-1} \mathrm{~s}^{-1}\) (c) \(\mathrm{s}^{-1}\) (d) \(\mathrm{L} \mathrm{mol}^{-1} \mathrm{~s}^{-1}\)

For a reaction \(1 / 2 \mathrm{~A} \longrightarrow 2 \mathrm{~B}\), rate of disappearance of ' \(\mathrm{A}\) ' is related to the rate of appearance of ' \(\mathrm{B}\) ' by the expression (a) \(-\frac{\mathrm{d}[\mathrm{A}]}{\mathrm{dt}}=\frac{1}{2} \frac{\mathrm{d}[\mathrm{B}]}{\mathrm{dt}}\) (b) \(-\frac{\mathrm{d}[\mathrm{A}]}{\mathrm{dt}}=\frac{1}{4} \frac{\mathrm{d}[\mathrm{B}]}{\mathrm{dt}}\) (c) \(-\frac{\mathrm{d}[\mathrm{A}]}{\mathrm{dt}}=\frac{\mathrm{d}[\mathrm{B}]}{\mathrm{dt}}\) (d) \(-\frac{\mathrm{d}[\mathrm{A}]}{\mathrm{dt}}=4 \frac{\mathrm{d}[\mathrm{B}]}{\mathrm{dt}}\)

The half life period of a first order chemical reaction is \(6.93\) minutes. The time required for the completion of \(99 \%\) of the chemical reaction will be $$ (\log 2=0.301) \text { : } $$ (a) \(23.03\) minutes (b) \(46.06\) minutes (c) \(460.6\) minutes (d) \(230.3\) minutes

The time for half life period of a certain reaction \(\mathrm{A} \longrightarrow\) products is 1 hour. When the initial concentration of the reactant 'A', is \(2.0 \mathrm{~mol} \mathrm{~L}^{-1}\), how much time does it take for its concentration to come from \(0.50\) to \(0.25 \mathrm{~mol} \mathrm{~L}^{-1}\) if it is a zero order reaction? (a) \(4 \mathrm{~h}\) (b) \(0.5 \mathrm{~h}\) (c) \(0.25 \mathrm{~h}\) (d) \(1 \mathrm{~h}\)

Consider the reaction: \(\mathrm{Cl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{~S}(\mathrm{aq}) \longrightarrow \mathrm{S}(\mathrm{s})+2 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq})\) The rate equation for this reaction is Rate \(=\mathrm{k}\left[\mathrm{Cl}_{2}\right]\left[\mathrm{H}_{2} \mathrm{~S}\right]\) Which of these mechanisms is/are consistent with this rate equation? [2010] (1) \(\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow \mathrm{H}^{+}+\mathrm{Cl}^{-}+\mathrm{Cl}^{+}+\mathrm{HS}^{-}\)(slow) \(\mathrm{Cl}^{+}+\mathrm{HS}^{2} \longrightarrow \mathrm{H}^{+}+\mathrm{Cl}^{-}+\mathrm{S}\) (fast) (2) \(\mathrm{H}_{2} \mathrm{~S} \Leftrightarrow \mathrm{H}^{+}+\mathrm{HS}^{-}\)(fast equilibrium) \(\mathrm{Cl}_{2}+\mathrm{HS}^{-} \longrightarrow 2 \mathrm{Cl}^{-}+\mathrm{H}^{+}+\mathrm{S}\) (slow) (a) 2 only (b) Both 1 and 2 (c) Neither 1 nor 2 (d) 1 only

The rate of a chemical reaction doubles for every \(10^{\circ} \mathrm{C}\) rise of temperature. If the temperature is raised by \(50^{\circ} \mathrm{C}\), the rate of the reaction increases by about: (a) 16 times (b) 42 times (c) 32 times (d) 20 times

For a first order reaction, (A) \(\rightarrow\) products, the concentration of A changes from \(0.10 \mathrm{M}\) to \(0.025\) Min 40 minutes. The rate of reaction when the concentration of \(\mathrm{A}\) is \(0.01 \mathrm{M}\), is: (a) \(3.47 \times 10^{-5} \mathrm{M} / \mathrm{min}\) (b) \(3.47 \times 10^{-4} \mathrm{M} / \mathrm{min}\) (c) \(1.73 \times 10^{-5} \mathrm{M} / \mathrm{min}\) (d) \(1.73 \times 10^{-4} \mathrm{M} / \mathrm{min}\)

The rate of a reaction doubles when its temperature changes from \(300 \mathrm{~K}\) to \(310 \mathrm{~K}\). Activation energy of such a reaction will be: \(\left(\mathrm{R}=8.314 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}\right.\) and \(\log 2=0.301\) ) (a) \(58.5 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (b) \(60.5 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (c) \(53.6 \mathrm{~kJ} \mathrm{~mol}^{-1}\) (d) \(48.6 \mathrm{~kJ} \mathrm{~mol}^{-1}\)

Deomposition of \(\mathrm{H}_{2} \mathrm{O}_{2}\) follows a first order reaction. In fifty minutes the concentration of \(\mathrm{H}_{2} \mathrm{O}_{2}\) decreases from \(0.5\) to \(0.125 \mathrm{M}\) in one such decomposition. When the concentration of \(\mathrm{H}_{2} \mathrm{O}_{2}\) reaches \(0.05 \mathrm{M}\), the rate of formation of \(\mathrm{O}_{2}\) will be: (a) \(6.93 \times 10^{-4} \mathrm{~mol} \mathrm{~min}^{-1}\) (b) \(2.66 \mathrm{~L} \mathrm{~min}^{-1}\) at \(\mathrm{STP}\) (c) \(1.34 \times 10^{-2} \mathrm{~mol} \mathrm{~min}^{-1}\) (d) \(6.93 \times 10^{-2} \mathrm{~mol} \mathrm{~min}^{-1}\)